Finally, we emphasize that hierarchical model decomposition, which provides an equivalent system representation composed of reduced-order models, cannot be obtained with standard model reduction techniques, such as the projection-based model reduction [1]} or the singular perturbation method through coordinate transformation [2]}.
Indeed, our idea relies on modification of the state space, which can make the dimension of the proposed representation larger than that of the original system, although the models used for designing each subcontroller are decomposed.
